Three tRNAs on the ribosome slow translation elongation

During protein synthesis, the ribosome simultaneously binds up to three different transfer RNA (tRNA) molecules. Among the three tRNA binding sites, the regulatory role of the exit (E) site, where deacylated tRNA spontaneously dissociates from the translational complex, has remained elusive. Here we...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 114; no. 52; pp. 13691 - 13696
Main Authors Choi, Junhong, Puglisi, Joseph D.
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 26.12.2017
Subjects
Binding sites
Biological Sciences
Codons
Correlation analysis
Elongation
Ionic strength
Kinetics
Molecules
Protein biosynthesis
Protein synthesis
Ribonucleic acid
Ribosomes
RNA
Transfer RNA
Translation
Translation elongation
Translocation
tRNA
nonfluorescent quencher
single-molecule FRET
protein synthesis
ribosome
E site
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Summary:During protein synthesis, the ribosome simultaneously binds up to three different transfer RNA (tRNA) molecules. Among the three tRNA binding sites, the regulatory role of the exit (E) site, where deacylated tRNA spontaneously dissociates from the translational complex, has remained elusive. Here we use two donor–quencher pairs to observe and correlate both the conformation of ribosomes and tRNAs as well as tRNA occupancy. Our results reveal a partially rotated state of the ribosome wherein all three tRNA sites are occupied during translation elongation. The appearance and lifetime of this state depend on the E-site tRNA dissociation kinetics, which may vary among tRNA species and depends on temperature and ionic strength. The 3-tRNA partially rotated state is not a proper substrate for elongation factor G (EF-G), thus inhibiting translocation until the E-site tRNA dissociates. Our result presents two parallel kinetic pathways during translation elongation, underscoring the ability of E-site codons to modulate the dynamics of protein synthesis.
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Contributed by Joseph D. Puglisi, November 10, 2017 (sent for review July 27, 2017; reviewed by Ruben L. Gonzalez Jr. and Michael Pavlov)
Author contributions: J.C. and J.D.P. designed research; J.C. performed research; J.C. contributed new reagents/analytic tools; J.C. and J.D.P. analyzed data; and J.C. and J.D.P. wrote the paper.
Reviewers: R.L.G., Columbia University; and M.P., Uppsala University.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1719592115